3. 



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4 



t 



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94 On Eledricity in Plants^ and on Vegeto-terrestrial Currents. 



r 



of common salt for examplej have obtained distinct effects (ope- 

 rating by throwing some drops of the solution on a plate of pla- 

 tinum raised to a white heat,) only at the instant when decrepita- 

 tion began, an effect announcing the volatilization of the last 

 portion of the water. 



As to the electric effects produced in vegetation, M. Pouillet 

 experimented as follows. Having placed upon a varnished 

 wooden table twelve glass capsules covered with varnish and 

 forming two ranges, he filled them with earth and connected 

 them together by means of platinum wire passing it from the in- 

 terior of one to the interior of another, and so on ; he then put 

 the system in communication with the superior plate of a con- 

 denser whilst the inferior plate was in connection with the soil. 

 Different grains were successively sown in the earth of the cap- 

 sules. During the first two days the grains swelled and the 

 germs came out of the envelop. The condenser gave no signs of 

 electricity. When the ^ 

 rating the two plates of the condenser, the two strips of gold- 

 leaf diverged, and evinced negative electricity. M. Pouillet 

 thence concluded that during the action of the oxygen of the air 

 on the amylaceous substance of the cotyledons, the gases which 

 are disengaged carry with them some positive electricity, and 

 leave in the young plant and consequently in the earth an excess 

 of negative electricity. Some hours were required to charge 

 anew the condenser. During the night and morning, the same 

 results were obtained, showing that light had no influence, which 

 is natural since light does not intervene in the first acts of vege- 

 table life. The experiments were made with wheat, grains o( 

 garden cress, and gillyflower, and the same results were obtained 

 for ten or twelve days. 



M. Pouillet has also observ^ed that when the growth of a plant 

 has been in progress three or four days, the condenser is charged 

 if by connection for a second only; — an effect due, according to 

 him to this, that the earth of the capsules becomes on drying 

 an imperfect conductor and so retains for some instants a portion 

 of disengaged electricity which serves to charge the condenser 

 at intervals. 



In all probability, the effect observed by M. Pouillet should be 

 attributed to the action of the oxygen of the air upon the carbon 

 of the amylaceous material of the grain, which is thereby changed 

 into sugar destined for the nutriment of the embryo during the 



J 



period 



M. Pouillet, in this first period, 



accord with the ordinary electrical states of the earth and atmo- 

 sphere : but are they produced also in the subsequent stages of 

 vegetation ? I think not, judging from facts to which I shall 

 soon refer. 



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